Transdermal diffusion cell testing is a very tedious procedure. The primary objective of the test is to study the penetration rate of a pharmaceutical compound or drug through skin. A common way to perform transdermal diffusion cell testing is by mounting a layer of skin or epidermis between a cell cap (donor) and a cell body (receptor). The skin or epidermis is bathed from below with a solution, typically an isotonic saline solution, injected into a chamber in a vessel having an opening against which the skin or epidermis is placed through a port in the vessel.
The temperature of the saline bathing solution is usually maintained in a temperature range of about 32° C. to about 37° C. by a thermostatically controlled water flow that enters a lower port of a water jacket around the chamber in which the saline bathing solution flows, and circulates out of the water jacket through an upper port. Warm water is supplied and circulated by two (upper and lower) manifolds that are connected to a constant temperature bath.
A homogeneous distribution of the temperature of the saline bathing solution is sought to be accomplished by the agitating motion of a Teflon-covered magnetic stirring bar, driven by an external magnet and mounted on a timing motor.
The cell cap is open to the air, exposing the skin or epidermis to the ambient conditions of the laboratory environment. The open cap also allows for a finite dose application of study compounds to the skin or epidermis by use of a micropipette or stirring rod.
During the test, the pharmaceutical compound or drug penetrates the skin or epidermis slowly and dissolves in the saline bathing solution. A syringe is used to pull out or sample the saline bathing solution for further analysis. Such tests are typically performed in groups of three cells, with a view toward averaging the test results.
Improvements in the vessel used for transdermal diffusion cell testing are always being sought.
Objects and Summary of the Invention
A vessel for use in transdermal diffusion cell testing in accordance with the invention includes a container defining an interior chamber having an opening at an upper end, and a casing arranged at least partially around and spaced apart from at least a portion of the container to thereby define a compartment therebetween. The chamber will be operatively used to retain a saline bathing solution, or other solution for the transdermal diffusion cell test, and therefore is not in flow communication with the compartment through which a temperature-regulating fluid, such as water, is circulated.
The vessel also includes a first inlet port and a first outlet port spaced apart from one another and each including a conduit communicating with the chamber. The first outlet port is arranged above the first inlet port and proximate the opening at the upper end of the chamber. The first outlet port is angled downward relative to a horizontal upper surface of the container against which skin, epidermis or other material being tested is placed. The first inlet port is at or near a bottom of the container such that solution can be directed into the chamber from a bottom of the chamber and fills the chamber from the bottom to its top.
The angular inclination of the first outlet port is designed to ensure that a conduit within the first outlet port is at a highest point of the chamber when the vessel is tilted so that air bubbles that might form during introduction of solution into the chamber would naturally move toward the highest point in the conduit, and then move from there through a conduit connected to the first outlet port to a waste receptacle. In this manner, air bubbles are automatically removed from the chamber without requiring manual intervention. That is, the tilting of the vessel may be performed automatically by a tilting mechanism connected to a plate on which the vessel is placed, which in combination with the inclination of the first outlet port relative to the container, causes movement of any air bubbles to the first outlet port and thus would not remain under the skin and adversely affect the diffusion of the pharmaceutical compound or drug through the skin into the solution. Tilting of the vessel may be performed prior to and/or simultaneously with introduction of solution into the chamber.
With the foregoing structure, the present invention significantly improves transdermal diffusion cell testing by eliminating the presence of air bubbles between the skin and the solution and thereby improving the testing results. Moreover, by maintaining the temperature of the solution in multiple vessels in a fixed range, a subsequent averaging of the test results from the vessels provides more accurate test results since variability in the temperature conditions of multiple vessels has been eliminated.
A method for introducing solution into an interior chamber of such a vessel including connecting a fill tube from a syringe pump to the first inlet port of the vessel, connecting the syringe pump to a solution source, orienting the syringe pump such that a syringe of the syringe pump has its inlet facing downward and its plunger vertically movable upward and downward, and controlling the syringe pump via a controller such that solution is drawn from the solution source through the syringe to the chamber in the vessel. In this manner, air bubbles in the solution drawn from the solution source enter into a chamber of the syringe and are thus prevented from entering into the chamber.
Variations and enhancements of this method are possible and include controlling the syringe pump to draw solution from the solution source and pass it to the chamber until the solution exits the chamber into the first outlet port, placing the vessel on a plate and while the syringe pump is controlled to pass solution into the chamber, tilting the plate to cause tilting of the vessel until a highest point of the chamber is situated in the conduit of the first outlet port such that any air bubbles against the skin enter into the conduit of the first outlet port. Additionally, a purge tube may be connected to the first outlet port of the vessel and the syringe pump controlled to pass solution into the chamber in the vessel until the solution exits the chamber into the first outlet port and flows into the purge tube. If the purge tube is connected to a drain pipe, the syringe may be controlled to pass solution into the chamber in the vessel until the solution exits the chamber into the first outlet port, flows into the purge tube and flows into the drain pipe.
An arrangement for conducting transdermal diffusion cell testing using the vessel described above includes a solution source fluidly coupled to each vessel, a waste receptacle fluidly coupled to each vessel, a syringe pump fluidly coupled to a respective vessel, and a sample collector fluidly coupled to the syringe pump(s). Each syringe pump is controlled to provide a first flow path of solution from the solution source to the waste receptacle through the associated vessel in order to fill the chamber with solution and to provide a second flow path of solution from the chamber to the sample collector.
Another arrangement for conducting transdermal diffusion cell testing using the vessels described above includes a plate arranged to receive or retain at least one vessel, a tilting mechanism coupled to the plate and arranged to tilt the plate, a fluid circulating mechanism that circulates a temperature-regulating fluid through the compartment via the second inlet and outlet ports, a sampling manifold including at least one sampling port, a respective sampling line connecting the first inlet port of a respective vessel to a respective sampling port on the sampling manifold, and at least one syringe insertable into the sampling manifold to enable sampling of solution in a respective vessel. The sampling manifold may be mounted onto the tilting mechanism.
Yet another arrangement for conducting automated transdermal diffusion cell testing using the vessels described above includes a controller, at least one drive console, each including a tilting mechanism that tilts the vessels and a fluid supply mechanism that supplies a regulating fluid to the compartment of each vessel, a sample collector, and at least one syringe pump assembly. Each syringe pump assembly including a plurality of syringes oriented with a plunger facing upward and an outlet downward, a structure for retaining the syringes, a mechanism for moving the plunger of each syringe in a controlled manner, and ports to enable connections of fluid conduits to the vessels to allow for flow of solution to and from the chambers in the vessels and to the sample collector. The controller controls each drive console, the sample collector and each syringe pump assembly to control flow of samples of solution from the vessels to the sample collector through the syringe pump assembly.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawings.